Not applicable.
(1) Field of the Invention
The present invention generally relates to a laser driven plasma antenna.
(2) Description of the Prior Art
The particular structure and configuration of an antenna system depends upon the particular frequency range with which the antenna is to be used. For example, antennas for use in the VLF (xe2x80x9cvery low frequencyxe2x80x9d), ELF (xe2x80x9cextremely low frequencyxe2x80x9d) or ULF (xe2x80x9cextremely low frequencyxe2x80x9d) ranges are significantly different in structure in comparison to antennas used in the VHF (xe2x80x9cvery high frequencyxe2x80x9d or UHF (xe2x80x9cultra high frequencyxe2x80x9d) ranges.
One typical prior art ELF antenna is the HED (xe2x80x9chorizontal electric dipolexe2x80x9d) antenna. However, typical HED antennas are inefficient. Furthermore, HED antennas must be located where large regions of low ground conductivity exists. Another prior art ELF antenna is the VED (xe2x80x9cvertical electric dipolexe2x80x9d) antenna. The VED antenna is generally more efficient than the HED, but is aerostat-supported unwieldy, and subject to xe2x80x9cblowdownxe2x80x9d which causes the antenna to assume the shape of a catenary.
What is needed is an antenna suitable for communications in the ULF, ELF and VLF ranges that eliminates the problems associated with conventional antennas that are used for such frequency ranges.
Therefore, it is an object of the present invention to provide an antenna system that addresses the foregoing problems.
Other objects and advantages of the present invention will be apparent to one of ordinary skill in the art in light of the ensuing description of the present invention.
In one aspect, the present invention is directed to a laser driven plasma antenna system. The antenna system comprises a laser that directs a laser beam toward the ionosphere so as to produce an ionized column of air, also referred to as xe2x80x9cplasma columnxe2x80x9d, that extends to the ionosphere. In one embodiment, the laser is a high powered laser. The laser drives electrons and ions upward by effecting the transfer of momentum from the photons to the electrons and ions. This transfer of momentum produces an upward current. Since the mass of the electrons is relatively insignificant in comparison to the ions, the electrons are the primary source of upward current. After an amount of time elapses, the electrons and the ions relax to equilibrium positions at different rates in a gravitational field. The relaxation of the ions and electrons is referred to as Maxwellian relaxation. The difference in relaxation rates of the electrons and ions produces a downward current. The laser is pulsed at a rate that corresponds to a frequency of interest. Thus, electromagnetic radiation having the frequency of interest is conducted through the ionized column of air as electrical current.
Several important features of the laser driven plasma antenna of the present invention are:
a) the laser produces the ionized column of air and the upward current simultaneously;
b) photon momentum and Maxwellian relaxations are used to produce current in a gravitational field; and
c) the ionized column extends between the laser and the ionosphere.
In one embodiment, the laser driven plasma antenna system comprises a laser having an output for emitting a laser beam that is directed toward the ionosphere so as to produce an ionized column of air extending between the laser and the ionosphere such that electromagnetic radiation is conducted through the ionized column of air as electrical current, and a pulsing circuit for pulsing the laser in accordance with a predetermined pulse rate that corresponds to a particular frequency of interest such that electromagnetic radiation having the particular frequency is conducted through the ionized column as electrical current having a frequency equal to the particular frequency of interest.
In a related aspect, the present invention is directed to a method of transmitting or receiving electromagnetic radiation, comprising the steps of providing a laser having an output for emitting a laser beam, directing the laser so that the laser beam is directed toward the ionosphere so as to produce an ionized column of air extending between the laser and the ionosphere such that electromagnetic radiation is conducted through the ionized column of air as electrical current, and pulsing the laser in accordance predetermined pulse rate that corresponds to a particular frequency of interest such that electromagnetic radiation having the particular frequency is conducted through the ionized column as electrical current having a frequency equal to the particular frequency of interest.